1. Field of the Invention
The present invention relates to an image capturing technique of deciding an exposure condition by calculating a photometric value for each object region.
2. Description of the Related Art
An image capturing apparatus such as a digital camera captures an image in real time and causes a display device to perform through-the lens display, thereby allowing the user to decide a composition while checking objects on a screen. In this case, it is possible to adjust the brightness of a display image, as needed, in accordance with an object by calculating a photometric value from the image captured for display and deciding an exposure condition so as to set the level of the photometric value to a target level. When the user presses the shutter button, it is also possible to decide an exposure condition for an image for recording by using the photometric value of the image captured for display.
However, when shooting a scene including objects with large brightness differences, for example, shooting a backlit person against the bright sky as a background, the apparatus may not appropriately perform photometry. Assume that the apparatus has performed exposure to set the brightness of a person to an appropriate level. In this case, the signal level of the sky may exceed the dynamic range of the image capturing device, and the signal may be saturated. It is not possible to obtain an appropriate photometric value from a region in which the signal is saturated. In contrast to this, assume that the apparatus has performed exposure with priority given to the sky so as inhibit the signal level of the sky from being saturated. In this case, since the apparatus shoots the person at a level lower than the appropriate level, the displayed person becomes dark.
There is known a method of composing two images upon respectively deciding exposure conditions from a relatively bright region and a relatively dark region in a screen when shooting a scene including objects with large brightness differences (see, for example, Japanese Patent No. 4105933). However, even the method disclosed in Japanese Patent No. 4105933 cannot decide an appropriate exposure condition when a signal from a bright region is saturated.
In addition, although there has been proposed a method of shooting a plurality of images with different brightnesses and adjusting brightness by composing the respective images, no consideration is given to a case of shooting one image or the brightness of an image for display.